| Year | Value | | 2018 | 58.17137201 | | 2017 | 57.16214635 | | 2016 | 50.32281787 | | 2015 | 42.68 | | 2014 | 40.26 | | 2013 | 37.5 | | 2012 | 34.74 | | 2011 | 32 | | 2010 | 30 | | 2009 | 21 | | 2008 | 14 | | 2007 | 8.28321982 | | 2006 | 6.808911008 | | 2005 | 6.074087107 | | 2004 | 5.31883207 | | 2003 | 4.324885391 | | 2002 | 3.518757175 | | 2001 | 2.685332713 | | 2000 | 1.822443852 | | 1999 | 1.159982461 | | 1998 | 0.472735008 | | 1997 | 0.24096792 |
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